3 3 . Solving Two-Step Equations Activity Modeling Two-Step Equations

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1 3 3 . Solving Two-Step Equations Activity Modeling Two-Step EquationsL E S S O N3 3.Solving Two-Step EquationsActivityModeling Two-Step EquationsA two-step equation is an equation you solve using two operations. You can use algebra tiles to model and solve two-step equations.Model and solve 2x + 3 = 7.x++++++1Model the equation 2x + 3 = 7.=x+++++x2Remove three 1-tiles from each side.=3The coefficient of x is 2, so divide the remaining tiles on each side into 2 identical groups.+x=4Keep one of these groups. One x-tile is equal to two 1-tiles. So, the solution is 2.x+=

2 3 3 . Solving Two-Step Equations In the Real WorldL E S S O N3 3.In the Real WorldMusic Club You pay $7 to join an Internet music club. You pay $2 for each song that you download. Your cost for joining and downloading some songs is $23. How many songs did you download?You will answer this question in Example 1 by solving the two-step equation 7 + 2x = 23. The value of x is the number of songs you downloaded.

3 3 3 . 1 Solving Two-Step Equations – 7 – 7L E S S O N3 3.EXAMPLE1Solving a Real-World ProblemYou pay $7 to join an Internet music club. You pay $2 for each song that you download. Your cost for joining and downloading some songs is $23. How many songs did you download?Costto joinper songNumberof songsTotal+=7 + 2x = 23Write an algebraic model.– 7– 7Subtract 7 from each side to undo addition.2x = 16Simplify.2x2162=Divide each side by 2 to undo multiplication.x = 8Simplify. x is by itself.ANSWERYou downloaded 8 songs.